Potentiometer



June 22, 1954 R. E. HARRISON ET AL POTENTIOMETER Filed Sept. 19, 1952 mm mm INVENTORS ROBERT E. HARRISON MARTHA COX .ATTORNE (7' Patented June 22, 1954 POTENTIOMETER Robert E. Harrison and Martha Cox, Indianapolis, Ind., assignors to the United States of America as represented by the Secretary of the Navy Application September 19, 1952, Serial No. 310,574

(Granted under Title 35, U. S. Code (1952),

sec. 266) 8 Claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to potentiometers and more particularly to a potentiometer having counter-rotating wiper arms for generating symmetrical resistance functions.

In the prior art to generate a symmetrical 180 degree resistance function it was necessary to carefully wind a resistance card of 180 degrees of arc symmetrically about the 90 degree point of the card.

To secure an accurate correspondence between the resistances equidistant from the 90 degree point of the resistance card presented a very difficult problem.

The present invention may bestated to consist generally of two counter-rotating discs, each carrying any number, n, of equally spaced contact members wiping against a resistance wound card extending l80+n degrees about the axis of the rotating discs. These will generate functions symmetrical about 212 points in the cycle. The illustrated example shows the use of 2 contacts on each disc and a resistance card of 90 degrees to generate functions symmetrical about the degree, 90 degree, 180 degree and 270 degree points.

It is an object of the present invention to provide a potentiometer which will generate a symmetrical resistance function about one or more positions.

Another object is to provide a potentiometer which will generate symmetrical functions without discontinuities.

Still another object is to provide a potentiometer which requires only one resistance wound card of 90 degrees of arc to generate a function symmetrical about four points of the cycle.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

The figure is a perspective view of an embodiment of the invention.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts, there is shown in the figure a potentiometer, generally designated by the numeral I0 comprising a supporting case M having end members I2 and I3 which carry bearings M and [5 in which is journaled a shaft IS, the end l3 also carries a resistance card i? insulated from the end member |3 and having a resistance proportional to the desired function wound thereon, said shaft It carries fixed thereto a member, which may be a gear, or a friction cone or disc, I8, and adjacent to member l8 a sleeve i9 is rotatably mounted on said shaft l6.

member 2| corresponding to member 18 and at the other end of sleeve I9 is mounted an insulat ing disc 22 carrying wiper contacts 23 and 24 in diametrical relation which in sequence make contact with resistance H, adjacent disc 22 there is fixed to the shaft IS a second insulating disc 25 which carries wiper contact members 26 and 21 in diametrical relation. Both discs 22 and 25 carry slip rings as shown at 23 on disc 22 which are electrically connected to contacts 23, 24 and 26, 21 respectively, and which are engaged by pick-up brushes 2S and 3| respectively. Members l8 and 2| have mounted between them a third member 32 of similar construction which is mounted on a fixed shaft 33, said member 32 forming a mechanical linkage between members l8 and 2| to rotate members I8 and 2| in opposite directions. The three members l8, 2| and 32 form a differential.

In operation the terminals of the resistance card I? are connected to a source potential (not shown) to produce a potential drop across the card.- The wiper contact 23, in the position shown, is just entering into engagement with the resistance card at the end 20 as contact 26 is leaving the card. As contact 23 reaches the end 3|] of the resistance card, contact 21, moving in the opposite direction, will engage the card at the end 30 simultaneously with contact 23 leaving the card and as contact 21 reaches the end 20 of the card, fartherest from its initial point of engagement, contact 24, which moves in the opposite direction, begins to engage the card at that point, end 26, and moves to end 30 to be followed in engagement with the card by contact 26, which moving in the opposite direction engages the card II at end 30 as contact 24 leaves the card. Thus as shaft I6 is continuously rotated in one direction contacts 23, 27, 24 and 26 successively engage alternate ends of resistance card l1, thereby transversing the card first in one direction then in the other. In order for the potentiometer to generate the function with the desired symmetry and continuity, contacts 29 and 3| are electrically connected.

In view of the above statements, it is obvious that the principles of this invention could be employed in such modifications as mounting the The sleeve i9- carries on the end adjacent the member IS a resistance card on a cylindrical housing about the shaft I6, and, by varying the length of the card I! and the number of contact arms, the resistance function may be varied symmetrically about particular points of are as the center and for various numbers of degrees on either side of the chosen center point.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A potentiometer having a case; a segmental resistance card covering not more than 180 'degrees of are mounted in said case; a shaft mounted concentric with said shaft; a differential connecting the shaft to the sleeve, one of said contact members being fixedly mounted on said sleeve and the other of said contact members being fixedly mounted on the shaft.

4. A device as claimed in claim 3 in which the means to establish electrical contact with the contact members comprises slip rings mounted one on each of the contact members in concentric relation to the shaft; brush contact members mounted on the case but insulated therefrom, one of said brushes engaging each of the slip rings respectively.

5. A device as claimed in claim 1 in which the means for producing counter-rotation of the contact members consist of said shaft; a sleeve mounted concentric with said shaft; a differential connecting the shaft to the sleeve, one of said contact members being fixedly mounted on said sleeve and the other of said contact members being fixedly mounted on the shaft.

6. A device as claimed in claim 1 in which the means to establish electrical contact with the contact members comprises slip rings mounted one on each of the contact members in concentric relation to the shaft; brush contact members mounted on the case but insulated therefrom; one of said brushes engaging each of the slip rings respectively.

7. A device as claimed in claim 1 in which said contact members includes a pair of insulating disc members carrying each disc one contact arm, said contact being arranged to simultaneously engage one end of the resistance card, and in which the means for producing counter-rotation of the contact members consist of said shaft; a sleeve mounted concentric with said shaft; a differential connecting the shaft to the sleeve, one of said contact members being "fixedly mounted on said sleeve and the other of said contact members being fixedly mounted on the shaft.

8. A device as claimed in claim 1 in which said contact members includes a pair of insulating disc members carrying on each disc two contact arms in diametrical relation to each other, and in which the means to establish electrical contact with the contact members comprises slip rings mounted one on each of the contact members in concentric relation to the shaft; brush contact members mounted on the case but insulated therefrom; one of said brushes engaging each of the slip rings respectively.

Name Date Hubbard Oct. 11, 1910 Number 

